Bentonite Slurry

ABSTRACT

There is provided an alkaline earth phyllosilicate material-containing slurry. It has been found the slurries of the present invention may be made at concentrations of up to 75% solids and remain pumpable. Broadly speaking, the slurry includes an alkaline earth phyllosilicate material and a polyfunctional compound and the remainder being water. The alkaline earth phyllosilicate material-containing slurry is preferably a pre-activated bentonite which is essentially semi-swollen upon addition to the slurry, and the polyfunctional compound is preferably an essentially non-monomeric, tall-oil derivative or distillate and the remainder being water. Other polyfunctional compounds include lignin, pitch, and liginosulfonate. The slurry does not requiring the addition of electrolyte. The properties of the slurry are such that the slurry contains between 5% and 75% total solid material in a pumpable form. There is also provided processes for making paper and for dewatering sludge using the slurry of this invention.

CROSS-REFERENCE TO RELATED APPLICATIONS

The contents of Provisional Application U.S. Ser. No. 60/749,237 filed Dec. 9, 2005, on which the present application is based and benefit claimed under 35 U.S.C. §119(e), is herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a phyllosilicate material slurry and to processes for using the slurry. More specifically, the invention relates to a bentonite slurry having increased solids and stability.

2. Description of Related Art

One use of bentonite clay slurries has been in the wet-end of the paper machines as an assisting agent to non-ionic and to cationic flocculants in the enhancement of water removal and retention of fine particles during papermaking. Additionally, mineral fibers have for a long time been added to pulp slurries to improve color, opacity, printability and other properties. One such method is disclosed in U.S. Pat. No. 3,052,595 wherein a mineral filler, such as kaolinite, titanium dioxide, talc and the like, bentonite, and an acrylamide polymer are added to a pulp slurry to improve filler retention. Another paper making process having improved retention of pulp components in paper is disclosed in U.S. Pat. No. 4,305,781 and is especially useful for making unfilled papers such as kraft, linerboard and newsprint. In this process the pulp suspension includes bentonite in an amount generally less than 5% Polyacrylamides are then added to the suspension to provide improvement in dewatering properties and fiber retention.

Usually the blentonite is brought to the paper mill in a dry form that is subject to “dusting” during handling. Expensive and cumbersome equipment must be employed to prepare a bentonite-containing slurry for introduction to the paper machine. It is expensive to automate such equipment, so that additional labor resources must be devoted to preparing the bentonite. A slurry or dispersion made off-site solves some of these problems. However, it is not economical or practical to ship clay suspensions as aqueous slurries because of the large amount of water. Attempts to increase the amount of bentonite in the slurry before shipping have not proven successful as bentonite in slurry form, at solids concentrations above 8% to 10%, is thixotropic, forming a gel-like or very viscous dispersion when prepared at above a few percent solids.

There have been repeated attempts to provide pumpable bentonite slurries but most attempts relate to uses in oilfield applications. In U.S. Pat. No. 5,779,785 there is disclosed a process for providing a clay slurry containing elevated solids that includes along with the clay a salt of a low molecular weight amine in an amount that is effective to prevent the clay from swelling; thus permitting the slurry to be stored and shipped. The inhibitinig effect of the amine salt is reversible upon subsequent dilution. Howvever, the patent does not address enhanced drainage and retention performance compared to the normal bentonite system starting with dry powder.

U.S. Pat. No. 6,045,657 is directed to paper making processes including microparticulate process which utilizes bentonite and provides the bentonite in the form of a concentrate at the paper mill. A cellulosic suspension is formed by diluting the bentonite slurry to 15% to 40% dry weight of bentonite in water. To the composition a citrate in a fluid stabilizing and activating amount is added. The resulting suspension has a viscosity below 5000 cps. A polymeric retention aid, such as a cationic starch may be mixed into the cellulosic suspension. While mention is made of the concentrates themselves no mention is made of their enhanced drainage and retention performance compared to the normal bentonite system starting with dry powder.

Despite the efforts of to produce a concentrated slurry, it remains desirable to provide an improved stable bentonite slurry with the handling characteristics of a pumpable viscosity range and an equivalent performance over the corresponding dry bentonite and/or higher solids than a normal bentonite in water slurry. Such slurry might also be designed to provide additional benefits during papermaking in the final application, such as sizing, water removal during pressing, or improved print quality of the finished paper.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an alkaline earth phylosilicate material-containing slurry having increased solids content and remains stable and pumpable over an extended period of time.

Another object of the present invention is to provide a bentonite-containing slurry that has increased solids content due to the inclusion of a polyfunctional compound.

A further object of the present invention is the provision of a process for using the slurry of the present invention in papermaking.

Yet another object of the present invention is to provide a process for using the slurry of the present invention in sludge dewatering.

The present invention is to an alkaline earth phylosilicate material-containing slurry. It has been found the slurries of the present invention may be made at concentrations of up to 75% solids and remain pumpable. Broadly speaking, the slurry includes an alkaline earth phylosilicate material and a polyfunctional compound and the remainder being water.

The alkaline earth phylosilicate material-containing slurry is preferably a pre-activated bentonite which is essentially semi-swollen upon addition to the slurry, and the polyfunctional compound is preferably an essentially non-monomeric, tall-oil derivative or distillate and the remainder being water. Other polyfunctional compounds include lignin, pitch, and lignosulfonate. The slurry does not require the addition of electrolyte. The properties of the slurry are such that the slurry contains between 5% and 75% total solid material in a pumpable form or in a gel which can be pumped upon breaking of the thixotropy. The slurries are time stable for over a month.

Another aspect of this invention is the provision of a process for making paper using the slurry of this invention. In another aspect of this invention there is provided a process for dewatering sludge using the high solids content slurry of this invention.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS(S)

The present inventions now will be described more fully hereafter. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather these embodiments are provided so that this disclosure will satisfy applicable legal requirements.

One aspect of the present invention is the provision of an alkaline earth phylosilicate material-containing slurry. It has been found the slurries of the present invention may be made at concentrations of up to 75% solids and remains stable and in a pumpable form or in a gel which can be pumped upon breaking the thixotropy. Broadly speaking, the slurry includes an alkaline earth phylosilicate material and a polyfunctional compound, such as an essentially non-monomeric, tall-oil derived blend of surfactants, and the remainder being water.

The preferred phylosilicate material used in the slurry of this invention is bentonite clay and may be one of the common commercially available bentonites (known as montmorillonite clays). Bentonites having the property of swelling in water are preferred. The bentonite clay should be pre-activated, i.e., subject to ion exchange whereby calcium and/or magnesium is replaced with sodium, which is essentially semi-swollen upon addition to the slurry, and further comprising water. The slurry is especially useful in applications where the pH between 3 and 10.

The polyfunctional compound is preferably a tall oil derivative or distillate. Tall oil is a natural mixture of rosin acids and fatty acids, together with unsaponifiable materials, which is obtained by acidifying the black liquor skimmings of the sulfate process of wood pulp manufacture, using resinous woods such as pine. The composition varies somewhat depending upon such factors as the species of the wood which was pulped. Crude tall oil acids generally contain from about 18% to 60% fatty acids, 28% to 66% rosin acids and 3% to 24% other constituents, notably unsaponifiable materials. Crude tall oil may be distilled and fractionated to separate the fatty acid and rosin acid fractions.

The polyfunctional compound used in the slurry may be distilled tall oil or at least one fatty acid from the distilled tall oil. Tall oil fatty acids normally consist of a major portion of mono-unsaturated oleic acids and diunsaturated linoleic acids (in approximately equal proportions), and small quantities of saturated acids and unsaponifiable. Since tall oil fatty acids are derived from tall oil which contains substantial quantities of rosin acids, small quantities of the latter may also be present. The U.S. Department of Commerce has accepted the definition of “tall oil fatty acids” as that material produced from crude tall oil which contains 90% or more free fatty acids. Most commercially available tall oil fatty acids contain substantially more than 90% fatty acids and substantially less than 10% rosin acids. Tall oil derivatives are reaction products of tall oil for use in various industries such as inks, paints, coatings, detergents and other surface active chemicals. Tall oil is dimerized and reacted with amines to yield polyamide resins for adhesives, inks, and coatings, Tall oil is saponified, esterified, or reacted with hydrophilic moieties. These products are useful as dispersants, detergents, surfactants, and other surface active chemicals.

Another preferred polyfunctional compound useful to make the concentrated slurry of high solids content is a rosin acid or rosin acid derivative. While the preferred rosin acid or rosin acid derivative is obtained from tall oil, it will be understood by those skilled in the art that the rosin acid may be obtained from other sources such as gum rosin. The rosin acids are a blend in a form-type that is solubilized, dispersed, and saponified, When the polyfunctional rosin acid derivative is present in a solid form it is finely dispersed, such that the particle size of the dispersed rosin is less than 2 μm, and preferably less than 0.5 μm. Rosin derivatives are products from a Diels-Alder reaction of rosin and fumaric acid or maleic anhydride. The resulting adducted species has a higher acid content and upon saponification yields a water soluble product.

The slurry may also include blends of acids selected from the group consisting of fatty acids and rosin acids. Preferably the rosin and fatty acid derivatives are the only dispersion stabilizers in the concentrated slurry.

Other polyfunctional compounds that may be used in the slurry of the present invention include lignin, pitch or lignosulfonates.

One advantage of the slurry of this invention is that the slurry is pumpable at high solids concentration, e. g., wherein the final inorganic solids are between 5% and 75% total solids, but preferably between 40% and 70% total solids. The slurry of this invention has a Hercules viscosity of the concentrate is below 100 cps (Bob: A, Spring: 200, 4400 rpm). This rheological profile is important in that under the shear conditions of a pump or the Hercules viscosity test the viscosity is low allowing for ease of use. The viscosity under low shear conditions, such as with Brookfield viscosity measurement is relatively high. Typical Brookfield viscosity for the present invention is approximately 200 cps (60rpm, #4spindle).

The phylosilicate material slurry is useful in any application where aqueous-compatible liquid-solid separation is the goal. For example, such potential uses are not limited to but may include applications in cellulosic fiber papermaking systems, sludge dewatering for water treatment (either influent or effluent), or other uses, for example, in mining or treating textiles.

As stated one aspect of the present invention is the provision of a process for making paper or paperboard that includes forming an aqueous cellulosic suspension comprising; a blend of an alkaline earth phylosilicate material and an amount of tall-oil derivative or distillate such that the final inorganic solids are between 5% and 75% and in which the Hercules viscosity of the concentrate is below 100 cps (Bob: A, Spring: 200, 4400 rpm); draining the suspension to form a sheet, and drying the sheet.

Another aspect of the present invention is a process for dewatering sludge that includes forming a high solids, pumpable slurry described by the present invention. The slurry is mixing with waste sludge and drained. The sludge may then be further handled by recovering or further processing or the like.

The present invention is illustrated by the following Examples.

EXAMPLE 1

A series of bentonite slurries were made with varying amounts of bentonite and a rosin blend. The rosin blend was STAFOR-50. The purpose of this example was to determine if the amount of bentonite solids could be increased in the slurry and still remain pumpable, that is have a sufficiently low viscosity. The slurries that were evaluated are shown in Table 1. TABLE 1 g STAFOR- % SOLIDS - % SOLIDS - RUN g BENTONITE g KOH g H2O 50 liquid BENT TOTAL 1 14 0 126  0 10 10 2 22 1 99 25 15 22 (FUMARATED) 3 22 1 99 25 15 22 (MALEINIZED) 4 31 1 75 50 20 36 (FUMARATED)

Viscosity Data for Above Runs: (Brookfield RV, Spindle 3 Speed 6) RUN VISCOSITY AFTFR 1 HR VISCOSITY AFTER 24 HRS 1 17,000 17,940 2 1700 3000 3 1400 2700 4 4000 4200

From the above data it appears that increasing the amount of Stafor-50 in the slurry allows increased solids to be achieved, and better time-stability. There is very little change from 1 hr to after 24-hrs in the slurry. Settling after 48 hrs. was minimal.

EXAMPLE 2 Slurry Made with Rosin/Fatty Acid Derivative Blend

% PC-SRK % liquid, % BENTONITE % % % sulfated fatty STAFOR- % SOLIDS - % SOLIDS - RUN as rec'd NaCl KOH H2O acid 50 liquid BENTONITE TOTAL 56-2 20 2 0 58 0 20 20 32 57-3 25 0 0 45 0 30 25 40 60-3 25 6 0 39 0 30 25 46 61-1 25 0 0.89 43.4 0.75 30 25 40

24 HR. Viscosity Data for Above Runs: (Brookfield RV, Spindle 4, Speed as Indicated). RUN VISCOSITY SPD 60 VISCOSITY SPD 6 56-2 1700 3500 57-3 3000 5500 60-3 too high too high 61-1 3700 3500

The significance of the above data is that the blend of tall-oil derived fatty and rosin compounds eliminates the need for added electrolyte. As well, the final compound, 61-1, has a rheology which is less shear-rate dependent, as the viscosity measured at 60 rpm is nearly the same as at 6 rpm. The product is easy to handle, flowable and stable.

EXAMPLE 3 Slurry Made with Lab-Cook of STAFOR-50

Rosin adduct was saponified according to normal procedures in the lab at 80° C., to which 2.8% based on bentonite solids of a fatty acid-derived dispersing aid was added ,MeadWestvaco PC-SRK. The bentonite was added to the solution at elevated temperature to see if this affected swelling. The slurry had a final total solids of 40% and a final viscosity after 1 hr of 4100, similar to Run 4 in Example 1 above. The slurry was stable after 4 days and still flowable with agitation on a stir plate.

Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. 

1. A slurry comprising a blend of alkaline earth phylosilicate material and a polyfunctional compound in an amount such that the final inorganic solids are between 5% and 75%.
 2. A slurry comprising a blend of a swellable clay and a polyfunctional tall-oil distillate or derivative is present in an amount such that the final solids are, between 5% and 75% total solids.
 3. The slurry according to claim 2 wherein said polyfunctional tall-oil distillate or derivative is present in an amount such that the final inorganic solids are between 40% and 70%.
 4. The slurry according to claim 2 wherein said swellable clay is bentonite.
 5. The slurry according to claim 2 wherein said tall-oil derivative comprises a blend of rosin acids in a form-type selected from a member of the group of types consisting of solubilized, dispersed, and saponified.
 6. The slurry according to claim 2 wherein said tall-oil derivative comprises at least one fatty acid.
 7. The slurry according to claim 2 wherein said tall-oil derivative comprises a blend of acids selected from the group consisting of fatty acids and rosin acids.
 8. The slurry according to claim 2 wherein said tall oil derivative is a polyfunctional rosin and said fatty acid derivative and is the only dispersion stabilizer in said slurry.
 9. The slurry according to claim 4 wherein said polyfunctional rosin derivative is present in solubilized form.
 10. The slurry according to claim 4 wherein said polyfunctional rosin derivative are present in a finely dispersed, solid form such that the particle size of the dispersed rosin is less than 2 μm.
 11. The slurry according to claim 1 wherein said polyfunctional compound is selected from the group consisting of lignin, pitch and lignosulfonate.
 12. The slurry according to claim 1 wherein said slurry has a Hercules viscosity of the concentrate is below 100 cps (Bob: A, Spring: 200, 4400 rpm).
 13. A high solids, pumpable slurry comprising: bentonite and a blend of essentially non-monomeric gum or tall-oil rosin, fatty acids, water, wherein said bentonite does not require activation and wherein electrolyte is added to the resulting slurry, and wherein the final slurry solids are between 5% and 75% total solids and in which the final 1-day Brookfield viscosity is below 3000 cps.
 14. The slurry according to claim 13 wherein said polyfunctional rosin and fatty acid derivatives are the only dispersion stabilizers in the concentrated slurry.
 15. The slurry according to claim 13 wherein said polyfunctional rosin derivatives are present in solubilized form.
 16. The slurry according to claim 13 wherein said polyfunctional rosin derivatives are present in a finely dispersed, solid form, such that the particle size of the dispersed rosin is less than 2 μm.
 17. A process for making paper or paperboard comprising: forming an aqueous cellulosic suspension, mixing a pumpable blend of an alkaline earth phylosilicate material and an amount of tall-oil derivative or distillate to form a dispersion such that the final inorganic solids are between 5% and 75% total solids draining the cellulosic suspension to form a wet sheet, and drying said sheet.
 18. The process according to claim 17 wherein said dispersion has a Hercules viscosity of below 100 cps (Bob: A, Spring 200, 4400 rpm).
 19. A process for dewatering sludge comprising: forming a high solids, pumpable slurry comprising: bentonite and a blend of essentially non-monomeric gum or tall-oil rosin, fatty acids, water, wherein said bentonite does not require activation, and wherein electrolyte is added to the resulting slurry and wherein the final slurry solids are between 5% and 75% total solids and in which the final 1-day Brookfield viscosity is below 3000 cps., mixing said slurry with waste sludge, draining said mixture to dewater, and disposing of said sludge. 